Safety means for power-driven chain saws

ABSTRACT

In a chain saw driven by an internal combustion engine a safety means comprising switch and brake means adapted to break the ignition current of the engine and stop the saw chain, and actuating means which is situated in a position in front of the handle of the saw and arranged to be operated by the hand of the operator in case of an accident to bring said switch and brake means into operation to stop the engine and the saw chain.

United States Patent Mattsson et al.

[451 May 23, 1972 [54] SAFETY MEANS FOR POWER-DRIVEN CHAIN SAWS [72]Inventors: Leif Erling M. Mattsson; Karl Garry Kenneth Fredriksson, bothof Brastad, Sweden [73] Assignee: Jonsereds Fabrikers Aktiebolag,Jonsered,

Sweden [22] Filed: Oct. 20, 1970 21 Appl. No.: 82,342

[30] Foreign Application Priority Data Oct. 29, 1969 Sweden ..14771 [52]US. Cl. ..l43/32 R, 143/17 C [51] Int. Cl ....B27b 17/02, 827g 19/00[58] Field ofSearch ..l43/32 R, 32 B, 32 D, 32 L, 143/43 R, 43 A, 17 C,157 R, 159 R [56] References Cited UNITED STATES PATENTS 1,189,6037/1916 Michener ..143/17 C UX 1,617,565 2/1927 Bens ..143/32 3,292,67312/1966 Gregory ..143/43 Primary ExaminerDonald R Schran Attomey-Karl W.Flocks ABSIRACT In a chain saw driven by an internal combustion engine asafety means comprising switch and brake means adapted to break theignition current of the engine and stop the saw chain, and actuatingmeans which is situated in a position in front of the handle of the sawand arranged to be operated by the hand of the operator in case of anaccident to bring said switch and brake means into operation to stop theengine and the saw chain.

6 Claims, 1 Drawing Figure SAFETY MEANS FOR POWER-DRIVEN CHAIN SAWS Thisinvention relates to safety means in power-driven chain saws whichcomprise an engine housing with a handle and a blade forming a guide fora saw chain driven by the engine via a drive wheel.

in certain circumstances, such as when felling is done at difficultyaccessible sites and under bad weather conditions, the handling of suchpower-driven chain saws is always associated with risks of accidents.Thus, the saw operator may slip for some reason or other, reaching outwith his hand so that it touches the rapidly moving saw chain. On sawingwith the pushing, i.e., non-pulling, chain run it may happen that thesaw is thrown back, particularly at the application thereof, if theengine has not been run up to full speed before application of the saw.Similar phenomena may occur on sawing with the pulling chain run, if theoutgoing run is jammed. For instance on trimming trees when the saw ismoved from below against a branch in an upward direction it has alsohappened that when the resistance to sawing suddenly ceases and theapplied pull is not simultaneously decreased, that the sword is abruptlythrown upwards so that the chain hits the saw operator in the head.

The object of the present invention is to provide safety means toprevent such accidents. To this end the safety means according to theinvention comprises a lever arm which is arranged to be swung about apivot axis and part of which is situated in front of the side of thehandle facing the blade and is spaced from the handle, a brake meansconnected to the lever arm and adapted, when the lever arm is swungabout the pivot axis, to be urged against a member driven by the engine,such as a member partaking in the rotation of the drive wheel, to brakesaid member and thus the saw chain, and actuating means arranged on thelever arm and adapted, when the lever arm is swung towards the blade, toactuate a switch for breaking the ignition current of the engine.

The invention will be described more in detail hereinbelow withreference to the accompanying drawing which illustrated a side elevationof a power-driven chain saw having safety means according to theinvention.

The power-driven chain saw illustrated in the drawing is a conventionalchain saw which can be modified by simple measures for easyincorporation of the safety means therein.

The chain saw comprises a housing 1 for an internal combustion engine(not shown). A drive wheel 4 for a saw chain 5 guided on the blade 6 iscoupled to the outgoing shaft 2 of the engine by a clutch 3. A U-shapedhandle 7 is mounted on the housing 1 and extends across the top of thehousing. A lever arm 8 is mounted on the housing for pivotment aboutjournals 9 so placed on the engine housing that the pivot axis of thelever arm 8 will be situated rearwardly of the handle 7. The lever arm 8includes a part 17 which is obliquely forwardly directed from the pivotaxis 9 and extends forwardly past the handle 7, and a part 18 which isbent at an angle obliquely upwardly away from said part 17 and issubstantially parallel to the corresponding lateral limb of the handle7. The outer end of the obliquely upwardly bent part 18 is thus situatedon the front side of the handle 7, Le, forwardly of the side of thehandle facing the blade 6. A rod is pivoted to the lever arm 8 andslidably guided in a guide in the engine housing, for example a boreformed in said engine housing and opening into an annular space betweenthe engine housing and the periphery of the clutch housing 3. Located insaid annular space is a brake shoe 11 which is connected to the rod 10and provided with a brake lining on the side facing the circumferentialsurface of the clutch housing 3. The lever arm 8 is normally kept in aposition of rest with the brake shoe 11 at some distance from theperiphery of the clutch housing 3 by a return spring 12 which is a coilspring wound about the rod 10 and interposed between the engine housing1 and the lever arm 8.

The lever arm 8 has a projection 13, for example at the angular bendbetween its two straight portions, to cooperate with a switch 14 locatedon the engine housing. The switch 14 is arranged and disposed in such amanner that by actuation of the switch the pro ection 13 breaks theignitlon current of the engine when the lever arm 8 is swung forwardlyand before the brake shoe 11 comes into braking engagement with theperiphery of the clutch housing 3.

At its outer end the lever arm 8 carries a rod 15 which extends acrossthe engine housing and is spaced such a distance from the handle 7 thatshould the saw operator's hand slip or move forward in any otherunintentional manner towards the lever arm 8 and the rod 15 or shouldthe saw as a result of a throw turn counterclockwise about the handle 7,the rod 15 actuated by the operators hand will be swung towards theblade, whereby the above described safety means comprising the switch 14and the brake means 10, 11 is made operative so that the ignitioncurrent of the engine is broken and in immediate conjunction therewiththe brake is applied for braking the living force of the engine,transmission and chain so that the chain is rapidly stopped.

The lever arm 8 may be in the form of a Ushaped member which surroundsthe upper part of the engine housing as does the U-shaped handle.Preferably, the lever arm is composed of two parts which are detachablyconnected together at 16. The brake rod 10 having the brake shoe 11 issecured to one part 17 of the lever arm as is the actuating means 13 forthe switch 14. The other part 18 of the lever arm carries the transverserod 15. In cases where the safety means 10, 11 and 14 is not desirableor where said means would impede a certain type of work, the upper part18 of the lever arm can be swung at the hinge connection 16 towards thehandle 7 so that the saw operator can move his hand freely.

What we claim and desire to secure by Letters Patent is:

1. In a power-driven chain saw having an engine housing with a handlethereon, and a blade forming a guide for a saw chain driven by aninternal combustion engine via a drive wheel, safety means comprising alever arm which is arranged to be swung about a pivot axis and part ofwhich is situated in front of the side of the handle facing the bladeand is spaced from said handle, a brake means connected to the lever armand adapted, when the lever arm is swung about the pivot axis, to beurged against a member driven by the engine, and actuating meansarranged on the lever arm and adapted, when the lever arm is swungtowards the sword, to actuate a switch for breaking the ignition currentof the engine.

2. Safety means as defined in claim 1, wherein the member driven by theengine is a member partaking in the rotation of the drive wheel for thesaw chain.

3. Safety means as defined in claim 1, wherein the pivot axis of thelever arm is disposed on the engine housing rearwardly of the handle.

4. Safety means as defined in claim 1, wherein the lever arm is composedof two parts so as to include a first part carrying said brake means andsaid actuating means for the switch, and a second part which is hingedto the first part and has a rod extending across the engine housing, andsaid second part can be swung about the hinge connection to a positionin which the rod is not in the way of the saw operators hand.

5. Safety means as defined in claims 1 and 2, wherein the brake shoe isconnected to a rod which is slidable in a guide connected to the enginehousing and pivoted to the lever arm.

6. Safety means as defined in claims 1, 3 and 5, wherein a return springis interposed between the lever arm and the engine housing to return thelever arm and the brake means to inoperative position.

1. In a power-driven chain saw having an engine housing with a handlethereon, and a blade forming a guide for a saw chain driven by aninternal combustion engine via a drive wheel, safety means comprising alever arm which is arranged to be swung about a pivot axis and part ofwhich is situated in front of the side of the handle facing the bladeand is spaced from said handle, a brake means connected to the lever armand adapted, when the lever arm is swung about the pivot axis, to beurged against a member driven by the engine, and actuating meansarranged on the lever arm and adapted, when the lever arm is swungtowards the sword, to actuate a switch for breaking the ignition currentof the engine.
 2. Safety means as defined in claim 1, wherein the memberdriven by the engine is a member partaking in the rotation of the drivewheel for the saw chain.
 3. Safety means as defined in claim 1, whereinthe pivot axis of the lever arm is disposed on the engine housingrearwardly of the Handle.
 4. Safety means as defined in claim 1, whereinthe lever arm is composed of two parts so as to include a first partcarrying said brake means and said actuating means for the switch, and asecond part which is hinged to the first part and has a rod extendingacross the engine housing, and said second part can be swung about thehinge connection to a position in which the rod is not in the way of thesaw operator''s hand.
 5. Safety means as defined in claims 1 and 2,wherein the brake shoe is connected to a rod which is slidable in aguide connected to the engine housing and pivoted to the lever arm. 6.Safety means as defined in claims 1, 3 and 5, wherein a return spring isinterposed between the lever arm and the engine housing to return thelever arm and the brake means to inoperative position.